1. Field of Invention
This invention relates to a direct access storage device in the form of a magnetic disc drive incorporating magnetic recording discs and movable recording and playback heads. This invention relates more particularly to apparatus for preventing unauthorized access to the data recorded upon such discs. While suitable for numerous types of such disc drives, this invention is particularly suited to disc drives in which at least one disc and one playback head are incorporated into an integral head/disc assembly.
2. Description of the Prior Art
In the past, direct access storage devices in the form of disc drives were designed and built in such a manner that the drive components and recording and playback heads formed an integral assembly, with the single recording disc or multiple disc packs being insertable into and removable from those drive structures. In those units sensitive data recorded upon the disc could easily be protected when not being used by simple removal of the disc or discs, conveniently in the form of an integral disc pack, from the drive, and then storage of those discs in a suitable security area or vault. This approach to security was reasonably satisfactory, although less than convenient in its requirement of removal of the recording discs.
The media removal technique of data security was still feasible, although less convenient, with the development of the "Winchester" technology in disc drives, as exemplified by the Memorex 3640 and IBM 3340 disc drives. These disc drives incorporated the recording and playback heads and the disc assemblies into a unitary data module which, although larger than a disc pack, was still readily removable and replaceable by an operator. Nonetheless, the increased size of the data modules pointed up the desirability of some data security arrangement which would not require removal of the module.
The problem of achieving data security became particularly acute with the next development in direct access storage device technology in which the discs and the heads are incorporated into an integral recording head/disc assembly (HDA) which is designed and configured for substantially permanent installation within the disc drive package, such that an operator could not readily remove the head/disc assembly (HDA). This arrangement is being used on equipment such as the Memorex 3650 and IBM 3350 storage devices. While performance of the storage device was improved by the enhanced alignment capabilities of the less readily removable or nonremovable HDA, such nonremovability made access to the data easier and precluded the use of a vault or other form of secured storage for data security. This problem is substantial, since the data stored in the HDA might be read out surreptitiously and since the HDA, while not readily removable by an operator, can be removed by a skilled technician. Thus, while the recording media (discs) were not readily removable, the HDA was capable of being used or removed, such that unauthorized removal or electronic access to the data might be obtained.